Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/26—Drying gases or vapours
  • B01D53/263—Drying gases or vapours by absorption
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
  • F24F3/00—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems
  • F24F3/12—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling
  • F24F3/14—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification
  • F24F3/1411—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification by absorbing or adsorbing water, e.g. using an hygroscopic desiccant
  • F24F3/1417—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification by absorbing or adsorbing water, e.g. using an hygroscopic desiccant with liquid hygroscopic desiccants
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
  • F24F5/00—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater
  • F24F5/0007—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater cooling apparatus specially adapted for use in air-conditioning
  • F24F5/001—Compression cycle type
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
  • F24F5/00—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater
  • F24F5/0007—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater cooling apparatus specially adapted for use in air-conditioning
  • F24F5/0014—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater cooling apparatus specially adapted for use in air-conditioning using absorption or desorption
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
  • F24F3/00—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems
  • F24F3/12—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling
  • F24F3/14—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification
  • F24F2003/144—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification by dehumidification only

Definitions

• the present invention is related to the field of environmental control systems and more particularly, to the field of systems which combine dehumidification and air conditioning. BACKGROUND OF THE INVENTION
• air conditioning systems not only reduce the temperature of the ambient air, but also remove substantial amounts of water from it. This is especially true when the air conditioner is treating "fresh" air inputted from outside the controlled environment.
• air conditioning/dehumidification is generally inefficient.
• the effective cooling capacity of the air conditioner is significantly reduced.
• U.S. Patent 4,984,434 describes an integrated system in which air to be cooled is first dehumidified by passing it through a desiccant type dehumidifier before being cooled by contact with an evaporator of an air conditioner. Regeneration of the desiccant is performed by passing the water containing desiccant over the condenser of the air conditioning system.
• This system suffers from a number of limitations. Firstly, it dehumidifies all of the air being cooled. Since most of the air inputted to the dehumidifier is from the controlled space (and thus fairly dry already) the dehumidifier does not remove much water from the air and thus does not provide much cooling for the condenser.
• a second problem is that such a system is not modular, namely, the dehumidifier must be supplied as part of the system. Furthermore, adding a dehumidifier to an existing air conditioning system and integrating the dehumidifier and air conditioner to form the system of this patent appears to be impossible.
• dehumidifying/air conditioning system Another type of dehumidifying/air conditioning system is also known.
• a dry desiccant is placed in the air input of the air-conditioner to dry the input air before it is cooled.
• Waste heat (in the form of the exhaust air from the condenser) from the air conditioner is then brought into contact with the desiccant that has absorbed moisture from the input air in order to dry the desiccant
• the amount of drying available from the desiccant is relatively low
• P ⁇ or art desiccant based dehurmdifiers generally require the movement of the desiccant from a first region in which it absorbs moisture to a second regeneration region
• this transfer is achieved by physically moving the desiccant from a dehumidifying station to a regeneration station, for example by mounting the desiccant on a rotating wheel, a belt or the like
• two pumps are generally provided, one for pumping the liquid to the regeneration station and the other for pumping the liquid from the regeneration station to the dehumidifying station
• a single pump is used to pump from one station to the other, with the return flow being gravity fed
• Fig 1 shows a chart of temperature vs. absolute humidity m which iso-enthalpy and iso-relative humidity curves are supenmposed Normal air conditioners operate on the principle of cooling the input air by passing it over cooling coils Assuming that the starting air conditions are at the spot marked with an X, the air is first cooled (curve 1) until its relative humidity is 100% at which point further cooling is associated with condensation of moisture m the air In order for there to be removal of liquid from the air, it must be cooled to a temperature that is well below a comfort zone 4 The air is heated to b ⁇ ng it to the comfort zone, generally by mixing it with warmer air already m the space being cooled This excess cooling m order to achieve dehumidification is a major cause of low efficiency in such systems, under certain conditions Normal dehumidifier systems actually heat the air while they remove air from it Du ⁇ ng dehumidification (
• An aspect of some preferred embodiments of the invention is concerned with a combined dehumidifier/air conditioner is which a relatively low level of integration is provided
• heat generated by the condenser is used to remove liquid from the desiccant
• the air conditioner condenser continues to be cooled by outside air
• the heated air which exits the air-conditioner, containing waste heat, is used to remo ⁇ e moisture from the desiccant
• a heat pump is utilized to transfer energy from relatively cool desiccant to heat the desiccant du ⁇ ng regeneration, in addition to the heat supplied from the exhaust of the air conditioning portion of the system This results in a system in which the air conditioner does not have to overcool the air to remove moisture and the dehumidifier does not heat the air m order to
• dehumidifier/ air-conditioner m which only "fresh", untreated air is subject to dehumidification p ⁇ or to cooling by the air conditioner This allows for both the dehumidifier and the air-conditioner to operate at high efficiency, since the dehumidifier ill be operating on only wet "fresh” air and the air conditioner will be cooling only relatively dry air
• the amount of waste heat generated by the air-conditioner is relatively high and the heat requirements of the dehumidifier are relatively low, since a major portion of the heat for regeneration is supplied by the heat pump.
• the air conditioner and dehumidifier are separate units without conduits for air connecting the units.
• the present invention provides advantages of utilizing waste heat from the air conditioner to provide regeneration energy for the dehumidifier
• moisture is transferred from the dehumidifier portion of a system to the regenerator without the necessity of transferring liquid from the regenerator back to the dehumidifier.
• moisture In general, in liquid dehumidifier systems, moisture must be transferred from the dehumidifier section to the regenerator section. Since the moisture is in the form of a moisture rich (low concentration) desiccant, this is performed by pumping or otherwise transferring the desiccant. Since the desiccant also contains desiccant ions, these must be returned to the dehumidifier to maintain the desiccant ion level required for dehumidification. This is generally achieved by pumping high concentration desiccant from the regenerator to the dehumidifier section. However, in addition to pumping ions, moisture is also transferred. While the extra energy utilized for pumping may or may not be significant, the inadvertent heat transfer implicit in pumping of the moisture back to the dehumidifier is significant in reducing the efficiency of the system.
• reservoirs in the dehumidifier and regenerator sections are connected with a passageway that allows only limited flow.
• the passageway takes the form of an aperture in a wall common to the two reservoirs.
• the absorption of moisture in the dehumidifying section increases the volume in the dehumidifier reservoir, resulting in the flow, by gravity, of moisture rich (low concentration) desiccant from the dehumidifier reservoir to the regenerator reservoir.
• This flow also carries with it a flow of desiccant ions, which must be returned to the dehumidifier section.
• this is achieved by pumping ion rich desiccant solution from the regenerator to the dehumidifier section.
• the return flow of ions is achieved, by diffusion of ions, via the aperture, from the high concentration regenerator reservoir to the low concentration reservoir.
• the inventors have found that, surprisingly, diffusion is sufficient to maintain a required concentration of ions in the dehumidifier section and that the return flow is not associated with an undesirable heat transfer associated with the transfer of (hot) moisture together with the ions, as in the prior art.
• no pumps are used to transfer desiccant between the reservoirs or between the dehumidifier section and the regenerator, in either direction.
• an air conditioning and dehumidifier system for controlling the environment of a controlled area, comprising: an air conditioner comp ⁇ sing a cooling unit in which air is cooled, a first inlet to the cooling unit drawing air from the area, a second mlet to the cooling unit drawing fresh air from outside the area, an outlet to the area via which cooled air is transferred to the area, a heat exchanger at which heat removed from air by the cooling unit is removed from the air conditioner, an air mlet to the heat exchanger into which relatively cool outside air is drawn, heat being transferred to said air from said heat exchanger, and a heated air outlet from the heat exchanger from which the heated air exits, a dehumidifying umt utilizing liquid desiccant, comp ⁇ sing a drying un t having a wet air mlet and a dry air outlet from which air d ⁇ ed by the drying unit exits and m which liquid desiccant d ⁇ es the air and removes heat
• a regenerator unit in which moisture removed from air by the drying unit is removed from the liquid desiccant, a hot air inlet to the regenerator unit, a wet air outlet from the regenerator unit via which air entenng the hot air inlet exits after moisture is transferred to it; and a heat pump that transfers heat from relatively cooler liquid desiccant m the dehumidifying unit to relatively warmer liquid desiccant, a conduit connecting the heated air outlet of the air conditioner to the hot air mlet of the dehumidifying, and a conduit connecting the dry air outlet of the dehumidifying unit to the second mlet of the air conditioner
• moisture removal from the desiccant is aided by providing heat to the regenerator
• the system includes at least one pump to pump desiccant between the drying unit and the regenerator
• the relatively cooler liquid desiccant is in a dehumidifier sump that receives desiccant after it has absorbed moisture from the outside air
• the drying unit comp ⁇ ses a chamber m which said moisture is removed from the outside air and wherein the heat is removed by the heat pump from liquid desiccant being transported to the chamber
• the drying unit comp ⁇ ses a dehumidifier sump that receives desiccant after it has absorbed moisture from the outside air and wherein the heat is removed by the heat pump from liquid desiccant being transported to the chamber from the sump
• the regenerator unit comp ⁇ ses a compartment that contains liquid desiccant being regenerated and wherein the heat is transfe ⁇ ed directly by the heat pump to said desiccant m said compartment
• the regenerator unit comp ⁇ ses a compartment that contains liquid desiccant being regenerated and wherein the heat is transferred by the at least one heat pump to liquid desiccant being transported to the compartment
• the regenerator unit compnses a regenerator sump that rece ⁇ es desiccant after moisture has been removed from it and wherein the heat is transferred to desiccant being transported to the chamber from the regenerator sump
• the air conditioner includes a fan to draw air mto the cooling unit and wherein the fan is also operative to draw air mto the wet air mlet of the drying unit
• the air conditioner includes a fan to draw air into the heat exchanger and wherein the fan is also operative to force air exiting the heat exchanger mto the hot air mlet of the regenerator
• the air conditioner utilizes a refrigerant to which heat is transferred m a condenser said cooling unit and from which refrigerant heat is transfe ⁇ ed m an evaporator in said heat exchanger
• the air conditioner cools an mte ⁇ or space and wherein the heat exchanger is outside the space
• the wet air mlet communicates to an area outside the controlled area
• the controlled area is at least a portion of a building
• the proportion of air drawn mto the cooling unit via the first and second mlets thereto is at least partially controllable
• a dehumidifier system comp ⁇ sing a liquid desiccant in two reservoirs, one of which contains a higher desiccant concentration than the other, a dehumidifier unit mto which moist air is introduced and from which less moist air is removed after dehumidification by liquid desiccant transfe ⁇ ed thereto, a regenerator unit which receives desiccant solution that has absorbed from the moist air and removes moisture from it, and a passageway connecting the reservoirs, ⁇ a which passageway, du ⁇ ng steady state operation of the dehumidifier, there is a net flow of moisture from the reservoir the low er desiccant concentration to the other reservoir without there being a net flow of desiccant ions through the passageway
• the passageway is an aperture such that the level of liquid desiccant in the two reservoirs is the same
• the two reservoirs include a first reservoir which receives said liquid desiccant from said dehumidifying chamber after said desiccant absorbs moisture thereat
• liquid desiccant is transferred to the dehumidifying chamber from the first reservoir
• the two reservoirs include a second reservoir which receives said liquid desiccant from said regenerator after removal of moisture therefrom
• liquid desiccant is transferred to the regenerating chamber from said second reservoir
• the dehumidifier includes a heat pump that transfers heat from relatively cooler liquid desiccant to relatively warmer liquid desiccant
• the heat pump pumps heat from the reservoir having the lower concentration of desiccant to that having the higher concentration of desiccant
• the heat pump transfers heat from desiccant in a conduit carrying desiccant to the dehumidifier unit
• a substantial temperature differential is maintained between the first and second rese ⁇ oirs
• the temperature differential is at least 5 °C
• the temperature differential is at least 10°C or at least 15°C
• Fig. 1 shows cooling and dehumidification curves for conventional air conditioning and dehumidification systems
• Fig. 2 schematically shows a dehumidifier unit, usable in a combined dehumidifying/ air-conditioning system, in accordance with a prefe ⁇ ed embodiment of the invention
• Fig. 3 schematically shows a second dehumidifier unit, usable in a combined dehumidifying/air conditioning system, in accordance with an alternative prefe ⁇ ed embodiment of the invention
• Fig. 4 schematically shows a dehumidifier unit system, in accordance with a prefe ⁇ ed embodiment of the invention, that is also usable in a dehumidifying/air-conditioning systems in accordance with a prefe ⁇ ed embodiment of the invention;
• Fig. 5 shows the dehumidification curves for the systems described with respect to Figs. 2-4, together with those for conventional air conditioning and dehumidification systems;
• Fig. 6 is a schematic diagram of a combined dehumidifier/air-conditioner system in accordance with a prefe ⁇ ed embodiment of the invention.
• the dehumidifiers described in applicants' PCT Applications PCT/IL97/00372, filed 16 November 1997 and PCT/IL98/00552, filed 11 November 1998, the disclosures of which are incorporated herein by reference, are used as dehumidifier 42. These applications were published on May 27, 1999 as WO 99/26025 and WO 99/26026 respectively. They were published after the filing of the application from which the present application claims priority and were incorporated by reference therein. In view of the utility of these dehumidifiers in the present invention, the dehumidifiers described therein are described in detail herein.
• a dehumidifying system 10 as described in the above referenced applications, comprises, as its two main sections a dehumidifying chamber 12 and a regenerator unit 32. Moist air enters dehumidifying chamber 12 via a moist air inlet 14 and dried air exits chamber 12 via a dry air outlet 16.
• desiccant 28 is pumped by a pump 20 from a desiccant reservoir 30 via a pipe 13 to a series of nozzles 22. These nozzles shower a fine spray of the desiccant into the interior of chamber 12, which is preferably filled with a cellulose sponge material 24 such as is generally used in the art for such purposes. More preferably, the desiccant is simply dripped on the sponge material. The desiccant slowly percolates downward through the sponge material into reservoir 30. Moist air entering the chamber via inlet 14 contacts the desiccant droplets. Since the desiccant is hygroscopic, it absorbs water vapor from the moist air and drier air is expelled through outlet 16.
• reservoir 30 is located on the bottom of chamber 12 so that the desiccant from sponge 24 falls directly into the reservoir.
• a pump 35 and associated motor 37 pump desiccant from an extension of reservoir 30 into pipe 13.
• a divider 38 receives desiccant from pipe 13 and sends part of the desiccant to nozzles 22 and part to regenerator unit 32.
• a valve or constriction 39 (preferably a controllable valve or constriction) may be provided to control the proportion of the desiccant which is fed to regenerator 32. If a controllable valve or constriction is used, the amount of desiccant is preferably controlled in response to the amount of moisture in the desiccant.
• Chamber 34 includes a heat exchanger 36 which heats the desiccant to drive off part of the water vapor it has absorbed, thus regenerating it.
• Regenerated liquid desiccant is transfe ⁇ ed back to reservoir 30 via a pipe 40 and a tube 42 of sponge material such as that which fills chamber 12.
• Tube 40 is preferably contained in a chamber 58 which has an inlet 60 and an outlet 62.
• Air generally from outside the area in which the air is being modified, for example from an air conditioning exhaust, as described below, enters the chamber via inlet 60 and carries away additional moisture which is evaporated from the still hot desiccant in tube 42.
• the air exiting at outlet 62 carries away this moisture and also moisture which was removed from the desiccant in the regenerator.
• a fan (not shown) at exit 62 sucks air from chamber 58.
• heat is transferred from the regenerated liquid desiccant to the desiccant entering or in the regenerator by bringing the two desiccant streams into thermal (but not physical) contact in a thermal transfer station (not shown).
• a heat pump may be used to transfer additional energy from the cooler desiccant leaving the regenerator to the hotter desiccant entering the regenerator, such that the desiccant returning to the reservoir is actually cooler than the desiccant which enters chamber 58.
• a heat pump system 44 is provided which extracts heat from the desiccant in reservoir 30 to provide energy to heat exchanger 36.
• this heat pump includes (in addition to exchanger 36 which is the condenser of the system) a second heat exchanger 46 in reservoir 30, which is the evaporator of the system, and an expansion valve 56.
• This transfer of energy results m a reduced temperature of the desiccant which contacts the air being d ⁇ ed thus reducing the temperature of the d ⁇ ed air
• this transfer of energy reduces the overall requirement of energy for operating the regenerator, generally by up to a factor of 3 Since the energy utilized by the regeneration process is the major energy requirement for the system, this reduction m energy usage can have a major effect on the overall efficiency of the system
• this method of heating of the desiccant in the regenerator may be supplemented by direct heating, utilizing a heating coil or w aste heat from an associated air-conditioner
• the proportion of w ater vapor in the desiccant in reservoir 30 and in the regenerated desiccant must generally be withm certain limits, which limits depend on the particular desiccant used
• a lower limit on the required moisture level is that needed to dissolve the desiccant such that the desiccant is in solution and does not crystallize
• the moisture level is monitored and controlled
• some desiccants are liquid even in the absence of absorbed moisture
• the moisture level m these desiccants need not be so closely controlled
• the regeneration process (which uses energy) should only be performed when the moisture level in the desiccant is above some level
• This monito ⁇ ng function is generally performed by measurement of the volume of desiccant, which increases with increasing moisture
• a prefe ⁇ ed method of measu ⁇ ng the volume of liquid m the reservoir is by measurement of the pressure in an inverted vessel 50 which has its opening placed m the liquid m the reservoir
• a tube 52 leads from vessel 50 to a pressure gauge 54
• the pressure measured by gauge 52 increases Since the volume of desiccant in the dehumidifier chamber and in the regenerator is fairly constant, this gives a good indication of the amount of desiccant and thus of the amount of moisture entrained m the desiccant
• the heat m chamber 34 is turned on In a prefe ⁇ ed embodiment of the invention, when the moisture level falls below some other, lower preset value, the heater is turned off
• heat pumps or other heat transfer means are provided to transfer heat from the d ⁇ ed air exiting chamber 12 and or from the heated moist air leaving regenerator chamber 34, to heat the desiccant on its way to or in chamber 34 If heat pumps are used, the source of the heat may be at a temperature lower than the desiccant to hich it is transfe ⁇ ed
• cooling of the desiccant m the reservoir can result m dned air leaving the dehumidifier which has the same, or preferably a lower temperature than the moist air ente ⁇ ng the dehumidifier, even p ⁇ or to any additional optional cooling of the dry air
• This feature is especially useful where the dehumidifier is used m hot climates in which the ambient temperature is already high
• one of the problems with dehumidifier systems is the problem of determining the amount of w ater in the desiccant solution so that the dehumidifier solution water content may be kept in a proper range
• a self regulating dehumidifier 100 that is self regulating with respect to water content of the desiccant solution and thus does not require any measurement of the volume or water content of the desiccant solution, is shown m Fig 3 Furthermore, the dehumidifier operates until a predetermined humidity is reached and then ceases to reduce the humidity, without any controls or cut-offs
• Dehumidifier 100 is similar to dehumidifier 10 of Fig 1, with several significant differences First, the system does not require any measurement of water content and thus does not have a volumet ⁇ c measure for the desiccant However, such a measurement may be provided as a safety measure if the solution becomes too concentrated
• the heat pump transfers heat between two streams of desiccant solution being transfe ⁇ ed from reservoir 30 (which is conveniently divided into two portions 30A and 30B connected by pipes 30C), namely a first stream being pumped to nozzles 22 by a pump system
• pipes 30C are designed so that its major effect is to generate a common level of the solution m portions 30A and 30B
• a temperature differential of 5°C or more is maintained, more preferably, 10°C or more and most preferably 15°C or even more.
• reservoir portion 30A is at a temperature of 30°C or more and reservoir portion 30B is at a temperature of l5°C or less.
• a different construction for regenerator unit 32 is shown, which is similar to that of the dehumidifier section.
• neither section has a cellulose sponge material. Such material may be added to the embodiment of Fig. 3 or it may be omitted from the embodiment of Fig. 2 and replaced by the spray mechanism of Fig. 3.
• spray nozzles are not used. Rather, the spray nozzles are replaced by a dripper system from which liquid is dripped on the cellulose sponge to continuously wet the sponge.
• a dripper system from which liquid is dripped on the cellulose sponge to continuously wet the sponge.
• heat pump system 44 extracts heat from the desiccant solution in conduit 102 and transfers it to the desiccant in conduit 104.
• Heat pump system 44 preferably contains, in addition to the components contained in the embodiment of Fig. 2, an optional heat exchanger 136 to transfer some of the heat from the refrigerant leaving heat exchanger 104 to the regenerating air.
• the compressor is also cooled by the regenerating air.
• additional air not used in the regenerator, may be used for cooling the compressor and the refrigerant. Alternatively, only such air is used for such cooling.
• the resultant heating of the air entering the regenerator increases the ability of the air to remove moisture from the desiccant.
• Heat pump 44 is set to transfer a fixed amount of heat. In a prefe ⁇ ed embodiment of the invention, the humidity set point is determined by controlling the amount of heat transfe ⁇ ed between the two streams.
• the regenerator is set up, such that at this same temperature and humidity, it removes the same amount of water from the desiccant solution. This may require an input of heat (additionally to the heat available from the heat pump). Further assume that the air entering the dehumidifier chamber has a lower humidity, for example 80%. For this humidity, less liquid is removed (since the efficiency of water removal depends on the humidity) and thus, the temperature of the desiccant solution leaving the dehumidifier chamber also drops. However, since less water enters the desiccant solution from the dehumidifier chamber, the amount of water removed from the solution in the regenerator also drops. This results in a new balance with less water removed and the desiccant solution at a lower temperature.
• a lower temperature desiccant results in cooler air.
• the temperature of the exiting air is also reduced.
• the relative humidity remains substantially the same. It should be understood that a reduction of input air temperature has substantially the same effect.
• the system is self regulating, with the dehumidifying action cutting off at some humidity level. The humidity level at which this takes place will depend on the capacity of the solution sprayed from nozzles 22 to absorb moisture and the ability of the solution and on the capacity of the solution sprayed from nozzles 22' to release moisture.
• the dehumidifier becomes less able to remove moisture from it.
• the solution is cooled on each transit through the conduit 102 and the percentage of desiccant in the solution in 30B reaches some level.
• the solution in 30A becomes more concentrated and less moisture is removed from it (all that happens is that it gets heated.
• both removal and absorption of moisture by the solution stop since the respective solutions entering the dehumidifier and regenerator chambers are in stability with the air to which or from which moisture is normally transfe ⁇ ed.
• this humidity point can be adjusted by changing the amount of heat transfe ⁇ ed between the solutions in conduits 102 and 104. If greater heat is transfe ⁇ ed, the desiccant in the dehumidifying chamber is cooler and the desiccant in the regeneration chamber is hotter. This improves the moisture transfer ability of both the dehumidifying chamber and the regenerator and the humidity balance point is lowered. For less heat pumped from the dehumidifier side to the regenerator side, a higher humidity will result. In addition, the set-point will depend somewhat on the relative humidity of the air entering the regenerator.
• Fig. 4 shows another dehumidifier 200, in which no pumping of desiccant is required. Except as described below 7 , it is generally similar to the dehumidifier of Fig. 3, except that there is no pumping of the desiccant liquid between the sumps 30A and 30B. (Fig. 4 does have a somewhat different layout from that of Fig. 3.) The inventors have surprisingly found that an approp ⁇ ately shaped and sized aperture, such as aperture 202 connecting the two sumps provides a suitable way to provide required transfer between the two sumps
• sump 30B (the sump of dehumidifying chamber 12) accumulates additional moisture over sump 30A (the sump of regenerator 32) This additional moisture must be transfe ⁇ ed to sump 30A or directly to the regenerator m order to remove the moisture from the desiccant
• concentration of desiccant in sump 30B is much lower than that m sump 30A, and the proportion of desiccant in sump 30A must be continually increased so that the efficiency and drying capacity of regeneration is kept high
• this aperture is chosen to provide transfer of ions of water and desiccant salt between the sumps without an undesirable amount of thermal transfer, especially from the hotter to the cooler reservoir
• the size of the aperture may be increased, such that at full dehumidification, the flow of heat between the sumps is at an acceptable level
• Undesirable heat flow may be determined by measu ⁇ ng the temperature near the hole and companng it to the temperature in the bulk solution in the sump
• the hole is too large, there will generally be a significant thermal flow from sump 3 OB to sump 30A
• the hole size is reduced too much, the transfer of ions is reduced and the overall efficiency is reduced
• Fig 4 preferably provides temperature differentials of the same order (or even greater) than that of Fig 3 While the size is preferably empmcally determined as desc ⁇ bed above, m an exemplary, but not limiting, expe ⁇ mental systems the aperture is rectangular, with rounded comers having a width of 1-3 cm (preferably about 2 cm) and a height of 1-10 cm. depending on the capacity of the system Preferably, the hole is placed at the bottom of the partition between the reservoirs, so as to take advantage of the higher salt concentration in the regenerator reservoir at the bottom of the reservoir The additional height allows the system to operate even under extreme conditions when some crystallization (which may block the aperture) occurs at the bottom of the reservoir
• the concentration of ions m reservoir 30A is generally higher than that m reservoir 3 OB This will be true, because the desiccant m 30A is continuously being concentrated and that m 30B is continuously be diluted This difference in concentration causes a diffusive flow of ions from reservoir 30A to reservoir 30B, via aperture 202 However, this is balanced by the flow of ions from reservoir 30B to 30A caused by the flow of solution this direction This results m no net flow of ions from one reservoir to the other Du ⁇ ng pe ⁇ ods of changing conditions of the input air, there may be a transient net flow of ions
• the temperature of the desiccant in reservoir 30B is 15°C and the concentration is 25% by weight of salt
• the salt used is lithium chlonde, since this is a stable salt with relatively high desiccating capacity Lithium bromide is an even better desiccant, but is less stable, it too can be used
• Other usable salts include magnesium chlonde. calcium chlonde and sodium chlonde
• Other liquid desiccants, as known m the art may also be used
• the temperature and concentrations for reservoir 30A is 400C and 35% It should be understood that the concentration in reservoir 30A can be higher (without crystallization) than that in reservoir 30B due to the higher temperature of the desiccant When the system stops, the concentrations and temperatures soon equalize Of course, these numbers will vary widely depending on the temperature and humidity of the air being conditioned and the "set point" of the dehumidifier (as determined by the heat pump setting), among other factors In the prefe ⁇ ed embodiment of the invention, there is no transfer of matenals between the reservoirs, except via the aperture and no pumps are used for transfer
• Fig 5 shows a diagram, similar to that of Fig 1 , except that the desiccant systems of Figs 2-4 are represented by a line 3
• the air treated by the dehumidifier need neither be cooled by the air conditioner (as the case of the desiccant systems of the pnor art) nor need it be heated as is necessary if air conditioning systems are used to remove the moisture
• Fig 6 is a block diagram of a combined dehumidifier/ air-conditioner system 310 in the context of a split air conditioner 312, such as is normally used to cool an enclosed area such as a large room 314 m a house Air conditioner 312, m its simplest form, comp ⁇ ses a room air mlet 316 which feeds room air via a conduit 318 to an evaporator 320 which cools the air Air from the room is drawn into evaporator 320 by a fan 322 and exists the evaporator via a room air outlet 324 to room 314
• a split air conditioner 312 such as is normally used to cool an enclosed area such as a large room 314 m a house Air conditioner 312, m its simplest form, comp ⁇ ses a room air mlet 316 which feeds room air via a conduit 318 to an evaporator 320 which cools the air Air from the room is drawn into evaporator 320 by a fan 322 and exists the evaporator via a room air
• Heated refrigerant is compressed by a compressor 324 (shown in an outside portion of air conditioner 312) and passed to a condenser 328 Condenser 328 is cooled by outside air drawn into a cooling mlet 330 by a fan 332. Heated air exits outside portion 326 via a waste heat outlet 334
• the cooled compressed refrigerant is expanded in an expander 336 and returns to evaporator 320 to be used to cool the room air.
• air conditioner 312 comp ⁇ ses a fresh air inlet 338 through which fresh air is brought in to the room
• the quantity of fresh air is generally controlled by a louver or baffle system 340, 341 Either one or both louvers or baffles 340, 341 may be supplied, depending on the amount and type of control over the proportion of fresh air required
• the fresh air is mixed with the air drawn from the room and is fed to evaporator 320
• Air conditioner 312, as desc ⁇ bed, is completely conventional m design In some preferred embodiments of the invention, other types of air conditioning systems may be used as appropnate
• a dehumidifier unit 342 is utilized to increase the efficiency and cooling capacity of the air-conditioner Dehumidifier 342, m a simplified block diagram comp ⁇ ses a drying unit 344 which receives outside air via a wet air mlet 346 and passes dned air out of a d ⁇ ed air outlet 348 The air is d ⁇ ed in unit 344 by passing it through a mist, or the like, of liquid desiccant or desiccant solution. Moisture m the air is adsorbed by the desiccant.
• dned air outlet 348 communicates with fresh air mlet 338 of air conditioner 312, preferably, via a conduit 349
• a conduit 349 Preferably, since the impedance of drying unit is relatively low, no air pump, additional to fan 322 of the air conditioner is required
• Desiccant with adsorbed water is transfe ⁇ ed to a regenerator 350 m which the desiccant is regenerated by removing moisture from it, by heating the desiccant
• this heating is accomplished by passing hot air through the desiccant (preferably the desiccant is m a mist or other finely divided form)
• the hot relatively dry air enters the dehumidifier via an mlet 352 and exits via an outlet 354
• This hot air is convemently and efficiently provided, m accordance with a prefe ⁇ ed embodiment of the invention, by connecting waste heat outlet 334 of air conditioner 312 with mlet 352 of the dehumidifier Since the pressure drop m regenerator 350 is very low, m preferred embodiments of the invention, no fan or other air pump in addition to fan 332 of air conditioner 312 is needed to move the air through the regenerator While, in a pref
• one of the systems of Figs 1-3 is used as dehumidifier 342
• port 348 of Fig 4 co ⁇ esponds to port 16 of Figs 1-3
• port 352 co ⁇ esponds to port 60
• port 346 co ⁇ esponds to port 14
• port 354 co ⁇ esponds to port 62
• dehumidifier 342 is shown m very schematic form in Fig 4 and that, for example, the placement of the elements may be different and many elements are not shown m Fig 4
• the pumps shown m Fig 4 are not present
• the heat-pumps of Figs 1-3 are not shown m Fig 4, although they are preferably present m the system
• dehumidifier 342 can be an add on to air conditioner 312, which may be a standard unit.
• the capacity of the air conditioner system for cooling is enhanced since it no longer needs to dry the air
• the efficiency of the combined unit actually increases with increasing temperature m contrast to normal air conditioner systems While the heat available is the heat developed by the air conditioner m cooling all of the air, the dehumidifier dnes only part of the air, namely that entenng the room This balance means that the heating requirements for the dehumidifier are generally easily met by the air conditioner exhaust
• Figs 3 and 4 the heat is pumped from liquid desiccant while it is being transported to the drying chamber. Alternatively, it could be removed from the liquid desiccant in a sump that receives carrier liquid from the drying chamber.
• Fig. 2 shows a different type of regenerator than does Figs. 3 and 4. In some prefe ⁇ ed embodiments of the invention, the regenerator types are interchangeable.
• Fig. 2 shows the heat being transfe ⁇ ed by the heat pump to the liquid in the regeneration chamber. Alternatively, or additionally, it can be transfe ⁇ ed to liquid desiccant being transported to the regeneration chamber (as in Figs. 3 and 4).

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